Scanning monochromators have been used for many decades to provide either a monochromatic source of light or to disperse the light emitted or reflected from a surface onto a detector. As such instrumentation has been made smaller to allow for portable use, the optical designs have undergone changes to allow for fewer parts to meet the requirements for compactness and weight reduction.
In a scanning spectrometer, a diffraction grating is rotated through a specified angle to bring the desired wavelengths to the detector. The bias is typically determined by swinging a shutter to cover the entrance slit at the end of each scan or, if the grating is rotated through 360° a blackened holder or light trap absorbs all the light entering the spectrometer so that nothing reaches the detector.
In a diode-array spectrometer, a solenoid-activated shutter at the entrance slit blocks the light from entering the spectrometer. The dark-current bias is different for each detector element in the array and the bias adjustment is stored and subtracted individually for each detector element in the control software. The amount of dark current is a function of the integration time and values are measured after the integration time has been determined based on the lighting situation.
When the spectrometer systems are miniaturized, there is less room to mount a solenoid or position a swinging shutter in a scanning spectrometer. In some cases a shutter cannot be accommodated for mechanical reasons.
Although present devices are functional, they are not sufficiently accurate or otherwise satisfactory. Accordingly, a system and method are needed to address the shortfalls of present technology and to provide other new and innovative features.